function for longest common substring?

[Ben <bench@xxxxxxxxxxxxxxx>]

Does anybody have a stored proc they'd like to share that computes the 
longest common substring for a set of strings? Wikipedia defines the 
problem nicely:

http://en.wikipedia.org/wiki/Longest_common_substring_problem

Basically, given "abcba" and "abdba", the algorithm should return "ab" and 
"ba" as equally valid answers.